Zoom lens and camera device incorporating the same

ABSTRACT

Provided are: a zoom lens which exhibits a large variable-power ratio, an increased degree of freedom with respect to aberration correction, and which has been achieved having a sufficient reduction in size in the optical axis direction; and an imaging device equipped therewith. The zoom lens includes at least, from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group, and a fifth lens group, in that order. In the zoom lens, prescribed conditions are satisfied.

FIELD OF THE INVENTION

The present invention relates to zoom lenses and camera devices incorporating the same, and more particularly, great magnification range, compact, light-weight, and high-speed focusing zoom lenses and camera devices incorporating the same.

BACKGROUND ART

For the recent years, camera devices, such as digital still cameras, employing solid state image sensors have become increasingly popular. In accordance with this, higher performance and miniaturized optics have been developed, which leads to a rapid popularization of much more downsized camera systems.

Evolution of optical systems toward much higher performance accordingly accelerates a demand for optical systems of much higher image quality and a demand for much greater magnification range optical systems, especially, extra great magnification range optical systems of which variable power ratio is greater than ×10. In addition, also strongly desired is downsizing not only of longitudinal extensions of optical systems along the optical axis but also of diameters of lens barrels; that is, optical systems satisfying all the needs and wants simultaneously are desired.

Prior art zoom lenses satisfying, to some extent, the needs and wants of higher image quality, greater magnification range, and downsizing, include a compact zoom lens that provides the maximal angle of view exceeding 70 degrees and a variable power ratio of approximately ×10 or even greater, and still yet attains a satisfactory image quality as well as appropriate focusing, which comprises five lens groups, namely, a first lens group G1 of positive refractivity, a second lens group G2 of negative refractivity, a third lens group G3 of positive refractivity, a fourth lens group G4 of negative refractivity, and a fifth lens group G5 of positive refractivity where upon varying its operative posture from the wide angle end to the telephoto end to vary magnification, distances between the first and second lens groups G1, G2 and between the third and fourth lens groups G3, G4 become greater while distances between the second and third lens groups G2, G3 and between the fourth and fifth lens groups G4, G5 become smaller, and the third lens group G3 or part or subset of the lens group are displaced to permit the zoom lens be in infinity focus (e.g., see Patent Document 1 listed below).

Some other zoom lenses satisfying the aforementioned needs and wants to some extent include that which provides variable power ratio as great as ×7 to ×10, F number as great as 2.5 to 4, and sufficiently high performance to serve as an optical system suitable for the up-to-date image pick-up devices with the smallest pixel pitch, which is designed as a very compact high variable power zoom lens system and comprises the foremost or first lens group (Gr1) of positive refractive power, the succeeding or second lens group (Gr2) of negative refractive power, the third lens group (Gr3) of positive refractive power, and the rearmost or fourth lens group (Gr4) of negative refractive power arranged in a series, meeting the requirements defined in the formula as follows:

1.1<f1/fT<2.5

where f1 is a focal length of the first lens group (Gr1), and fT is a focal length of the whole optical system of the zoom lens photographing at its telephoto end (T) (e.g., see Patent Document 2 listed below).

Further other zoom lenses satisfying the aforementioned needs and wants to some extent include a zoom lens system that is sufficiently compact to incorporate in video cameras, digital still cameras, lens-integrated cameras, and the like, optimized for high-speed auto-focusing, and of enhanced image quality, which comprises the foremost or first positive power lens group, the succeeding or second negative power lens group, the third positive power lens group, the fourth negative power lens group, the fifth positive power lens group, and the rearmost or sixth negative power lens group arranged in a series where distances between the adjacent pairs of the lens groups are varied to vary power, meeting the requirements defined in the formulae as follows:

DW(1-2)<DT(1-2)  (1)

DW(2-3)>DT(2-3)  (2)

DW(3-4)>DT(3-4)  (3)

DW(4-5)<DT(4-5)  (4)

DW(5-6)<DT(5-6)  (5)

where DW(i-j) is a distance between the i-th and j-th lens groups when the zoom lens system photographing at its wide-angle end is in infinity focus, DT(i-j) is a distance between the i-th and j-th lens groups when the zoom lens system at its telephoto end is in infinity focus; and the fourth lens groups being displaced along the optical axis for focusing (e.g., see Patent Document 3 listed below).

LIST OF THE DOCUMENTS OF THE RELATED ART Patent Documents 1 to 3

JPN Pat. Preliminary Publication of Unexamined Pat. Appl. No. 2001-091833

JPN Pat. Preliminary Publication of Unexamined Pat. Appl. No. 2001-350093

JPN Pat. Preliminary Publication of Unexamined Pat. Appl. No. 2006-251462

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The aforementioned prior art zoom lenses have their lens groups for zooming increased in number to enhance the freedom of compensating for aberrations, thereby enhancing the image quality throughout the zooming range. As to the zoom lens system disclosed in Patent Document 1, however, providing the variable power ratio as much as ×10, it is not satisfactorily reduced in dimension along the optical axis.

Meanwhile, as to the zoom lenses disclosed in Patent Documents 2 and 3, successfully attaining the enhanced image quality by virtue of the displaceable lens groups increased in number, they provide a variable power ratio so unsatisfactorily small as to meet the demand for greater magnification range. They are also insufficient in reducing the dimension along the optical axis.

Object of the Invention

The present invention is made to overcome the aforementioned disadvantages in the prior art zoom lenses, and accordingly, it is an object of the present invention to provide a zoom lens attaining an enhanced variable power ratio, increased freedom of compensating for aberrations, and satisfactory downsizing along the optical axis, and also provide a camera device incorporating the same.

Solutions to the Problems with the Prior Art 1st Aspect of the Invention

In one aspect of the present invention, provided is a zoom lens comprising at least five lens groups, namely, the first lens group of positive refractive power, the second lens group of negative refractive power, the third lens group of positive refractive power, the fourth lens group, and the fifth lens group serially arranged in order on the closest to an object first basis, meeting the requirements defined in the formulae as follows:

2.0<βrt<3.5  (1)

0.8<frt/ft<−0.3  (2)

where βrt is a composite lateral magnification of the lens groups behind the third lens group and closer to the image plane than the same while the zoom lens takes an operative posture at its telephoto end, frt is a composite focal length of the lens groups behind the third lens group and closer to the image plane while the zoom lens takes an operative posture at its telephoto end, and ft is a focal length of the zoom lens at the telephoto end.

In the first aspect of the present invention, it is especially preferable that there are five or more lens groups, namely, the first positive power lens group, the second negative power lens group, the third positive power lens group, and the fourth and fifth lens groups, and distances between the adjacent pairs of the lens groups and distances between convergence positions of rays from the adjacent pairs of the lens groups are varied during the zooming.

Effect of the Invention in the 1st Aspect

The first aspect of the present invention permits a zoom lens design that successfully attains an enhanced variable power ratio, increased freedom of compensating for aberrations, and sufficient downsizing along the optical axis.

Especially, the zoom lens thus designed to have five or more lens groups such as the first positive power lens group, the second negative power lens group, the third positive power lens group, the fourth and fifth lens groups, and/or the like can have distances between the adjacent pairs of the five or more lens groups and distances between convergence positions of rays from the adjacent pairs of the same respectively varied to enhance the freedom of compensating for aberrations.

The effect of the invention in the first aspect will now be compared with those of the inventions disclosed in the aforementioned prior art patent documents. A telephoto ratio of the zoom lens taking an operative posture at the telephoto end, namely, a ratio of the overall length to the focal length of the zoom lens is 1.12 in Embodiment 1 of the present invention in the first aspect and the smallest of all, i.e., 1.87 in the second embodiment of the invention in Patent Document 1, 2.36 in the fourth embodiment of the invention in Patent Document 2, and 1.24 in the sixth embodiment of the invention in Patent Document 3.

It will be appreciated from this that the present invention in the first aspect is beneficial in downsizing the overall length of the zoom lens upon photographing at the telephoto end.

2nd Aspect of the Invention

According to the second aspect of the present invention, provided is a camera device that incorporates image pick-up devices in position closer to the image plane of the zoom lens in the first aspect of the present invention for receiving an optical image produced by the zoom lens and converting it into electric signals.

Effect of the Invention in the 2nd Aspect

The second aspect of the present invention permits a zoom lens design that exploits the features of the aforementioned zoom lenses in the first and second aspects of the present invention to attain a more compact, more light-weight, higher-speed focusing zoom lens and provides a camera device incorporating such a zoom lens.

Embodiment 1 of the Invention

In the context of the present invention in the first aspect, the second lens group meets the requirements defined in the formula as follows:

3.5<βt/γ2w<8.0  (3)

where β2t is a lateral magnification of the second lens group in the zoom lens focusing telephoto, and β2w is a lateral magnification of the second lens group in the zoom lens focusing wide angle. Embodiment 2 of the Invention

In the context of the present invention in the first aspect, upon shifting its operative posture from the wide-angle end to the telephoto end to vary magnification, the zoom lens focusing wide angle has its first lens group displaced closer to an object to photograph than it is focusing telephoto.

Embodiment 3 of the Invention

In the context of the present invention in the first aspect, the fourth lens group exhibits negative refractive power.

Embodiment 4 of the Invention

In the context of the present invention in the first aspect, the fourth lens group is displaced toward the image plane for shifting the zoom lens from a state of being in infinity focus to another state of being in focus on an object within close-up photographing range.

Embodiment 5 of the Invention

In the context of the present invention in the first aspect, the lens groups behind the third lens group and closer to the image plane than the same meet the requirements defined in the formula as follows:

2.2<frw/f2<3.4  (4)

where frw is a composite focal length of the lens groups behind the third lens group and closer to the image plane, and f2 is a focal length of the second lens group.

Embodiment 6 of the Invention

In the context of the present invention in the first aspect, the fifth lens group exhibits negative refractive power.

Embodiment 7 of the Invention

In the context of the present invention in the first aspect, the sixth lens group of positive refractive power is disposed immediately behind the fifth lens group and closer to the image plane.

Description of the Formula (1)

Meeting the requirements defined in the formula (1), the zoom lens can ensure an appropriate back focal distance or back focus upon taking an operative posture at the telephoto end.

When βrt is smaller than the lower limit defined in the formula (1), a lateral magnification of the lens groups closer to the image plane becomes smaller, which leads to insufficient downsizing of the diameter of the zoom lens.

When βrt exceeds the upper limit defined in the formula (1), a magnification rate derived from the lens groups closer to the image plane becomes so great as it is needed to have a greater number of lens pieces dedicated to the compensation for aberrations, which will hinder the downsizing in a longitudinal dimension.

Description of the Formula (2)

When frt/ft is smaller than the lower limit defined in the formula (2), a composite focal length of the lens groups closer to the image plane becomes greater, or in other words, the back focus considering telephoto ratio becomes greater, which results in an increase in the overall length of the zoom lens upon focusing telephoto.

When frt/ft exceeds the upper limit defined in the formula (2), the composite focal distance of the lens groups closer to the image plane becomes excessively small, or in other words, the back focus considering telephoto ratio becomes excessively small. Resultantly, it is needed to have an increased number of lens pieces dedicated to the compensation for aberrations, which will hinder the downsizing in a longitudinal dimension.

Description of the Formula (3)

When β2t/β2w is smaller than the lower limit defined in the formula (3), the second lens group contributes less to variation in magnification, and this makes it difficult to enhance variable power ratio of the zoom lens as a whole.

When β2t/β2w exceeds the upper limit defined in the formula (3), the second lens group causes excessive variation in magnification, and it is unavoidable to have an increased number of lens pieces, which will hinder the downsizing in a longitudinal dimension.

Description of the Formula (4)

Correction of distortion aberration developed in the zoom lens upon focusing wide angle is facilitated by appropriately adjusting the ratio of a composite focal distance of the lens groups behind the third lens group and closer to the imaging plane to a focal distance of the second lens group. As the second lens group comes to predominant in power, the second lens group permits stronger negative distortion to occur. Thus, it is desirable to achieve an optical power balance in which the lens groups closer to the imaging plane develop positive distortion to facilitate cancellation of the negative distortion.

When frw/f2 is smaller than the lower limit defined in the formula (4), specifically, when the lens groups closer to the image plane come to excessively predominant in power, the compensation for curvature of field is difficult.

When frw/f2 exceeds the upper limit defined in the formula (4), specifically, when the lens groups closer to the image plane are inferior in power, these lens groups fail to develop sufficient positive distortion, and this hinders the whole lens system from cancelling the negative distortion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross sectional view illustrating lens optics in a first embodiment of a zoom lens according to the present invention, with the zoom lens taking an operative posture at the wide-angle end;

FIG. 2 depicts graphs of spherical aberration, astigmatism, and distortion developed in the first embodiment of the zoom lens photographing at the wide-angle end and in infinity focus where the graph of spherical aberration includes broken line for the g-line (435.8 nm in wavelength) and alternate dash and dot line for the C-line (656.3 nm) while the graph of astigmatism includes solid line for sagittal image plane and broken line for meridional image plane, and all the graphs of the aberrations in the succeeding drawings follow the style;

FIG. 3 depicts graphs of spherical aberration, astigmatism, and distortion developed in the first embodiment of the zoom lens extended to the intermediate focal distance and in infinity focus;

FIG. 4 depicts graphs of spherical aberration, astigmatism, and distortion developed in the first embodiment of the zoom lens extended up to the telephotographing focal distance and in infinity focus;

FIG. 5 is a vertical cross-sectional view illustrating a second embodiment of the zoom lens according to the present invention, with the zoom lens taking an operative posture at the wide-angle end;

FIG. 6 depicts graphs of spherical aberration, astigmatism, and distortion developed in the second embodiment of the zoom lens photographing at the wide-angle end and in infinity focus;

FIG. 7 depicts graphs of spherical aberration, astigmatism, and distortion developed in the second embodiment of the zoom lens extended to the intermediate focal distance and in infinity focus;

FIG. 8 depicts graphs of spherical aberration, astigmatism, and distortion developed in the second embodiment of the zoom lens extended up to the telephotographing focal distance and in infinity focus;

FIG. 9 is a vertical cross-sectional view illustrating a third embodiment of the zoom lens according to the present invention, with the zoom lens taking an operative posture at the wide-angle end;

FIG. 10 depicts graphs of spherical aberration, astigmatism, and distortion developed in the third embodiment of the zoom lens photographing at the wide-angle end and in infinity focus;

FIG. 11 depicts graphs of spherical aberration, astigmatism, and distortion developed in the third embodiment of the zoom lens extended to the intermediate focal distance and in infinity focus;

FIG. 12 depicts graphs of spherical aberration, astigmatism, and distortion developed in the third embodiment of the zoom lens extended up to the telephotographing focal distance and in infinity focus;

FIG. 13 is a vertical cross-sectional view illustrating a fourth embodiment of the zoom lens according to the present invention, with the zoom lens taking an operative posture at the wide-angle end;

FIG. 14 depicts graphs of spherical aberration, astigmatism, and distortion developed in the fourth embodiment of the zoom lens photographing at the wide-angle end and in infinity focus;

FIG. 15 depicts graphs of spherical aberration, astigmatism, and distortion developed in the fourth embodiment of the zoom lens extended to the intermediate focal distance and in infinity focus; and

FIG. 16 depicts graphs of spherical aberration, astigmatism, and distortion developed in the fourth embodiment of the zoom lens extended up to the telephotographing focal distance and in infinity focus.

BEST MODE OF THE INVENTION

In conjunction with the following description of embodiments of the present invention, various optical data of parameters are used; that is, surface number NS denotes the n-th surfaces of individual lens pieces in a series counted on the closest to an object first basis, R denotes a radius of curvature of each of the surfaces of the lens pieces, D is a distance along the optical axis between any of the adjacent pairs of the surfaces of the lens pieces, Nd denotes a refractive index for the d-line (wavelength λ=587.6 nm), and vd is an Abbe number for the d-line (wavelength λ=587.6 nm). In addition, the surface number succeeded by STOP designates an aperture stop. The surface number succeeded by ASPH indicates an aspherical surface of which radius of curvature R in the optical parameter table is a paraxial curvature radius.

Embodiment 1

A first embodiment of the zoom lens according to the present invention comprises, as shown in FIG. 1, the first lens group G1 of positive refractive power, the second lens group G2 of negative refractive power, the third lens group G3 of positive refractive power, the fourth lens group G4 of negative refractive power, the fifth lens group G5 of negative refractive power, and the sixth lens group G6 of positive refractive power serially arranged in order on the closest to an object first basis.

The first lens group G1 is comprised of a cemented lens of two lens pieces, namely, a negative power meniscus lens piece L1 the closest to the object and having its convex surface faced toward the object and a positive power lens piece L2, and a positive power meniscus lens piece L3 farther from the object and having its convex surface faced toward the object.

The second lens group G2 is comprised of a negative power meniscus lens piece L4 the closest to the object and having its front side shaped in aspherical surface and its rear side shaped in intensely in-curved concave surface, a lens piece L5 the second closest to the object and having its opposite sides shaped in concave surface, a lens piece L6 having its opposite sides shaped in convex surfaces, and a negative power meniscus lens piece L7 the farthest from the object and having its concave surface faced toward the object.

The third lens group G3 is comprised of a lens piece L8 the closest to the object and having its opposite sides shaped in aspherical convex surface, a lens piece L9 having its opposite sides shaped in concave surface, and a lens piece L10 the farthest from the object and having its opposite sides shaped in convex surface.

The fourth lens group G4 is comprised of a cemented lens of two lens pieces, namely, a lens piece L14 closer to the object and having its opposite sides shaped in convex surface and a lens piece L11 having its aspherical surface faced toward the image plane and its front and rear sides shaped in concave surface.

The fifth lens group G5 is comprised of a negative power meniscus lens piece L12 having its concave surface faced toward the image plane.

The sixth lens group G6 is comprised of a positive power meniscus lens piece L13 having its convex surface faced toward the image plane.

The zoom lens in the first embodiment, upon varying its operative posture from the wide angle end to the telephoto end to vary magnification, has its first lens group displaced toward the object, its second lens group traversed along the trajectory first coming closer to and then apart from the image plane, its third lens group displaced toward the object, its fourth lens group traversed relative to the third lens group along the trajectory first coming closer to and then apart from the image plane, its fifth lens group displaced toward the object, and its sixth lens group kept stationary relative to the image plane.

Focusing on an object within close-up photographing range is conducted by displacing the fourth lens group toward the image plane.

The optical data of parameters on the zoom lens in the first embodiment are given as follows:

TABLE 1 NS R D Nd νd  1 63.6829 1.3000 1.91048 31.31  2 36.5043 0.0100 1.57046 42.84  3 36.5043 5.9600 1.49845 81.61  4 −852.9715 0.2000  5 34.2606 4.0000 1.62032 63.39  6 151.8569 D(6)   7 ASPH 54.3406 0.2000 1.51700 49.96  8 54.6285 0.8000 1.91695 35.25  9 8.9090 4.0317 10 −30.8661 0.6500 1.91695 35.25 11 23.5188 0.4000 12 17.7113 2.9807 1.93323 20.88 13 −28.4855 0.7683 14 −16.2247 0.6000 1.77621 49.62 15 −51.4542 D(15) 16 STOP 0.0000 1.2000 17 ASPH 9.1792 2.8596 1.58547 59.46 18 ASPH −21.2748 0.3952 19 −469.2779 0.5000 1.89461 30.74 20 11.3473 1.6070 21 27.4927 3.2402 1.59489 68.62 22 −9.5668 D(22) 23 48.0920 1.2000 1.81263 25.46 24 −93.4000 0.0100 1.57046 42.84 25 −93.4000 0.6000 1.80558 45.45 26 ASPH 13.0486 D(26) 27 −12.9322 0.6300 1.81263 25.46 28 −18.8160 D(28) 29 −147.0832 1.9501 1.73234 54.67 30 −35.3238 9.8000 31 0.0000 2.8000 1.51872 64.20

In the above table of the optical data of parameters, any of aspherical surfaces identified by their respective surface numbers succeeded by ASPH can be expressed by the following equation:

X(y)=(y ² /R)/[1+(1−e·y ² /R ²)^(2/2) ]+A4·y ⁴ +A6·y ⁶ +A8·y ⁸ +A10·y ¹⁰

where X(y) is a distance (or a sagittal) from the apex of the aspherical surface to the center of the base of the asphere along the optical axis relative to the height y perpendicular to the optical axis, R is a radius of curvature (or a paraxial curvature radius) of the reference spherical surface, c is a constant of the cone, and A4, A6, A8 and A10 are constants of the aspherical surfaces.

The optical data of parameters on the aspherical surfaces are given as follows:

TABLE 2 ASPH ε A4 A6 A8 A10 7 1.0000  1.91163e−005 −4.04139e−007  3.49343e−009 −1.49337e−011 17 1.0000 −1.14585e−004  4.99824e−006 −1.46840e−007 −1.08200e−009 18 1.0000  4.60442e−004  5.38067e−006 −2.32614e−007  0.00000e+000 26 1.0000 −6.79774e−006 −5.35988e−008  4.43501e−009 −9.66065e−011

Further given below is a varied distance between the specified adjacent pair of the surfaces of the lens pieces during the zooming in its various stages, that is, with the zoom lens staying at the wide-angle end (f=10.30 mm) being extended to the intermediate focal distance (f=30.47 mm) and up to the telephoto end (f=97.97 mm), and vice versa, together with a focal distance f (in millimeters), F number Fno, and an angle of field ω.

TABLE 3 f 10.30 30.47 97.97 Fno 3.6490 5.0069 5.7049 ω 40.281 11.231 4.671 D(6) 0.9300 15.4076 32.7201 D(15) 20.1523 7.8284 1.9719 D(22) 1.2330 2.6313 1.5000 D(26) 7.2929 5.8946 7.0259 D(28) 0.4190 11.1985 17.2290

Still further given below is a varied distance between the surfaces of the lens pieces from a state where the zoom lens in focus on an object within close-up photographing range stays at the wide-angle end (f=10.30 mm) to another state of its being extended to the intermediate focal length (f=30.47 mm) and up to the telephoto end (f=97.97 mm), together with a focal length f (in millimeters) of the zoom lens in infinity focus and a distance D(0) (in millimeters) from the object to photograph to the foremost or first lens surface:

f 10.30 30.47 97.97 D(0) 920.28 903.19 889.86 D(22) 1.2704 3.3008 2.9038 D(26) 7.2555 5.2251 5.6221

Embodiment 2

A second embodiment of the zoom lens comprises, as shown in FIG. 5, the first lens group G1 of positive refractive power, the second lens group G2 of negative refractive power, the third lens group G3 of positive refractive power, the fourth lens group G4 of negative refractive power, the fifth lens group G5 of negative refractive power, and the sixth lens group G6 of positive refractive power serially arranged in order on the closest to an object first basis.

The first lens group G1 is comprised of a cemented lens of two lens pieces, namely, a negative power meniscus lens piece L1 the closest to the object and having its convex surface faced toward the object and a positive power lens piece L2, and a positive power meniscus lens piece L3 having its convex surface faced toward the object.

The second lens group G2 is comprised of a negative power meniscus lens piece L4 the closest to the object and having its aspherical surface faced toward the object and its rear side shaped in intensely in-curved concave surface, a lens piece L5 the second closest to the object and having its opposite sides shaped in concave surface, a lens piece L6 having its opposite sides shaped in convex surface, and a negative power meniscus lens piece L7 the farthest from the object and having its concave surface faced toward the object.

The third lens group G3 is comprised of a lens piece L8 the closest to the object and having its opposite sides shaped in aspherical convex surface, a negative power lens piece L9 having its concave surface faced toward the image plane, a cemented lens of two lens pieces, namely, a lens piece L10 having its aspherical surface faced toward the object and its opposite sides shaped in convex surface and a negative power meniscus lens piece L11 having its concave surface faced toward the object, and another cemented lens of two lens pieces, namely, a negative power meniscus lens piece L12 having its concave surface faced toward the image plane and a lens piece L13 having its opposite sides shaped in convex surface.

The fourth lens group G4 is comprised of a cemented lens of two lens pieces, namely, a lens piece L14 closer to the object and having its opposite sides shaped in convex surface and a lens piece L15 having its opposite sides shaped in concave surface.

The fifth lens group G5 is comprised of a negative power meniscus lens piece L16 having its concave surface faced toward the image plane.

The sixth lens group G6 is comprised of a positive power meniscus lens piece L17 having its convex surface faced toward the image plane.

The zoom lens in the second embodiment, upon varying its operative posture from the wide angle end to the telephoto end to vary magnification, has its first lens group displaced toward the object, its second lens group traversed along the trajectory first coming closer to and then apart from the image plane, its third lens group displaced toward the object, its fourth lens group traversed relative to the third lens group along the trajectory first coming closer to and then apart from the image plane, its fifth lens group displaced toward the object, and its sixth lens group kept stationary relative to the image plane.

Focusing on an object within close-up photographing range is conducted by displacing the fourth lens group toward the image plane.

The optical data of parameters on the zoom lens in the second embodiment are given as follows:

TABLE 4 NS R D Nd νd  1 71.8184 1.3000 1.91048 31.31  2 38.1169 0.0100 1.57046 42.84  3 38.1169 4.5000 1.49845 81.61  4 −271.5053 0.2000  5 34.2543 3.5128 1.62032 63.39  6 144.7606 D(6)  7 ASPH 51.0704 0.2000 1.51700 49.96  8 43.5620 0.7600 1.91695 35.25  9 9.1890 3.7360 10 −21.5757 0.6040 1.91695 35.25 11 29.1538 0.4000 12 20.4299 2.7524 1.93323 20.88 13 −21.6790 0.7155 14 −12.4871 0.5960 1.77621 49.62 15 −39.8843 D(15) 16 STOP 0.0000 1.2000 17 ASPH 10.5362 2.8018 1.58547 59.46 18 ASPH −22.5427 0.2000 19 158.7690 0.5000 1.83945 42.72 20 12.7924 1.5947 21 ASPH 43.3184 2.3000 1.58547 59.46 22 −12.8698 0.0100 1.57046 42.84 23 −12.8698 0.4670 1.91048 31.31 24 −21.0076 0.8760 25 64.1680 0.4670 1.91695 35.25 26 15.3783 0.0100 1.57046 42.84 27 15.3783 3.0765 1.62032 63.39 28 −13.0505 D(28) 29 41.5408 1.3000 1.81263 25.46 30 −58.6162 0.0100 1.57046 42.84 31 −58.6162 0.4830 1.80831 46.50 32 12.0837 D(32) 33 −15.2307 0.6300 1.81263 25.46 34 −23.6034 D(34) 35 −87.2068 1.9569 1.73234 54.67 36 −27.2049 9.8000 37 0.0000 2.8000 1.51872 64.20

The optical data of parameters of the aspherical surfaces are given as follows:

TABLE 5 ASPH ε A4 A6 A8 A10 7 1.0000 2.99229e−005 −2.77911e−007 4.08113e−009 −6.45590e−012 17 1.0000 −9.24021e−005 −2.03212e−006 1.09833e−007 −3.07901e−009 18 1.0000 2.42296e−004 −3.20842e−006 1.17483e−007 −3.05003e−009 21 1.0000 −1.20912e−005 −1.01954e−006 2.87946e−008 −2.68033e−010

Further given below is a varied distance between the specified adjacent pairs of the surfaces of the lens pieces during the zooming in its various stages, that is, with the zoom lens staying at the wide-angle end (f=11.22 mm) being extended to the intermediate focal distance (f=63.64 mm) and up to the telephoto end (f=145.52), and vice versa, together with a focal distance f (in millimeters), F number Fno, and an angle of field ω.

TABLE 6 f 11.22 63.64 145.52 Fno 3.6414 5.3644 5.7509 ω 37.997 9.208 3.170 D(6) 0.9300 21.8749 36.7527 D(15) 18.6221 4.8769 1.4250 D(28) 1.1900 4.2490 1.0100 D(32) 8.8421 5.7832 9.0221 D(34) 0.8860 15.9875 20.1532

Still further given below is a varied distance between the surfaces of the lens pieces from a state where the zoom lens in focus on an object within close-up photographing range stays at the wide-angle end (f=11.22 mm) to another state of its being extended to the intermediate focal length (f=63.64 mm) and up to the telephoto end (f=145.52 mm), together with a focal length f (in millimeters) of the zoom lens in infinity focus and a distance D(0) (in millimeters) from the object to photograph to the foremost or first lens surface:

f 11.22 63.64 145.52 D(0) 918.76 896.55 880.86 D(28) 1.2267 4.6723 3.4247 D(32) 8.8054 5.3598 6.6074

Embodiment 3

A third embodiment of the zoom lens comprises, as shown in FIG. 9, the first lens group G1 of positive refractive power, the second lens group G2 of negative refractive power, the third lens group G3 of positive refractive power, the fourth lens group G4 of negative refractive power, the fifth lens group G5 of negative refractive power, and the sixth lens group G6 of positive refractive power serially arranged in order on the closest to an object first basis.

The first lens group G1 is comprised of a cemented lens of two lens pieces, namely, a negative power meniscus lens piece L1 the closest to the object and having its convex surface faced toward the object and a positive power lens piece L2, and a positive power meniscus lens piece L3 having its convex surface faced toward the object.

The second lens group G2 is comprised of a negative power meniscus lens piece L4 the closest to the object and having its front side shaped in aspherical surface and its rear side shaped in intensely in-curved concave surface, a lens piece L5 the second closest to the object and having its opposite sides shaped in concave surface, a lens piece L6 having its opposite sides shaped in convex surface, and a negative power meniscus lens piece L7 the farthest from the object and having its concave surface faced toward the object.

The third lens group G3 is comprised of a lens piece L8 the closest to the object and having its opposite sides shaped in aspherical convex surface, a negative power lens piece L9 having its concave surface faced toward the image plane, a cemented lens of two lens pieces, namely, a lens piece L10 having its aspherical surface faced toward the object and its opposite sides shaped in convex surface and a negative power meniscus lens piece L11 having its concave surface faced toward the object, and another cemented lens of two lens pieces, namely, a negative power meniscus lens piece L12 having its concave surface faced toward the image plane and a lens piece L13 having its opposite sides shaped in convex surface.

The fourth lens group G4 is comprised of a cemented lens of two lens pieces, namely, a lens piece L14 closer to the object and having its opposite sides shaped in convex surface and a lens piece L15 having its opposite sides shaped in concave surface.

The fifth lens group G5 is comprised of a negative power meniscus lens piece L16 having its concave surface faced toward the image plane.

The sixth lens group G6 is comprised of a positive power meniscus lens piece L17 having its convex surface faced toward the image plane.

The zoom lens in the third embodiment, upon varying its operative posture from the wide angle end to the telephoto end to vary magnification, has its first lens group displaced toward the object, its second lens group traversed along the trajectory first coming closer to and then apart from the image plane, its third lens group displaced toward the object, its fourth lens group traversed relative to the third lens group along the trajectory first coming closer to and then apart from the image plane, its fifth lens group displaced toward the object, and its sixth lens group kept stationary relative to the image plane.

Focusing on an object within close-up photographing range is conducted by displacing the fourth lens group toward the image plane.

The optical data of parameters of the zoom lens in the third embodiment are given as follows:

TABLE 7 NS R D Nd νd  1 109.0553 1.5000 1.90366 31.31  2 52.5697 0.0100 1.56732 42.84  3 52.5697 5.5700 1.49700 81.61  4 −146.2327 0.2000  5 39.5728 3.9700 1.61800 63.39  6 112.3407 D(6)  7 ASPH 79.0234 0.2000 1.51460 49.96  8 65.0676 0.9000 1.91082 35.25  9 12.3717 4.1854 10 −23.8730 0.7500 1.91082 35.25 11 42.3962 0.4930 12 28.5426 3.3730 1.92286 20.88 13 −24.6589 1.0150 14 −14.8587 0.7500 1.77250 49.62 15 −49.5781 D(15) 16 STOP 0.0000 1.5000 17 ASPH 13.2954 3.2480 1.58313 59.46 18 ASPH −32.0948 0.2000 19 62.5251 0.6200 1.86188 42.08 20 15.8491 2.0200 21 ASPH 61.7390 2.8500 1.58313 59.46 22 −15.2253 0.0100 1.56732 42.84 23 −15.2253 0.6000 1.90766 33.41 24 −25.8791 1.0200 25 109.2068 0.5800 1.91082 35.25 26 20.0859 0.0100 1.56732 42.84 27 20.0859 3.7247 1.61882 64.32 28 −16.2282 D(28) 29 51.3428 1.6830 1.80518 25.46 30 −75.7267 0.0100 1.56732 42.84 31 −75.7267 0.6000 1.80420 46.50 32 15.6073 D(32) 33 −18.5559 0.9000 1.80518 25.46 34 −28.5021 D(34) 35 −152.2485 2.3543 1.72916 54.67 36 −38.5471 11.0000  37 0.0000 4.2000 1.51680 64.20

The optical data of parameters on the aspherical surfaces are given as follows:

TABLE 8 ASPH ε A4 A6 A8 A10 7 1.0000 1.19556e−005 −5.12224e−008 4.21707e−010 2.89639e−012 17 1.0000 −4.81203e−005 −6.04617e−007 2.40398e−008 −4.15344e−010 18 1.0000 1.17843e−004 −9.32847e−007 2.61092e−008 −4.24829e−010 21 1.0000 −5.75515e−006 −1.80638e−007 2.44731e−009 −5.43340e−012

Further given below is a varied distance between the specified adjacent pairs of the surfaces of the lens pieces during the zooming in its various stages, that is, with the zoom lens staying at the wide-angle end (f=14.43 mm) being extended to the intermediate focal distance (f=57.85 mm) and up to the telephoto end (f=145.40 mm), and vice versa, together with a focal distance f (in millimeters), F number Fno, and an angle of field ω.

TABLE 9 f 14.43 57.85 145.40 Fno 3.6708 5.4085 5.9148 ω 37.102 10.651 3.671 D(6) 1.1330 24.2823 41.7003 D(15) 21.7353 5.4909 1.7000 D(28) 1.4374 6.0872 3.6419 D(32) 12.1029 7.4531 9.8984 D(34) 1.0300 19.1189 24.8250

Still further given below is a varied distance between the surfaces of the lens pieces from a state where the zoom lens in focus on an object within close-up photographing range stays at the wide-angle end (f=14.43 mm) to another state of its being extended to the intermediate focal length (f=57.85 mm) and up to the telephoto end (f=145.40 mm), together with a focal length f (in millimeters) of the zoom lens in infinity focus and a distance D(0) (in millimeters) from the object to photograph to the foremost or first lens surface:

f 14.43 57.85 145.40 D(0) 901.52 876.67 857.15 D(28) 1.5087 6.7510 6.5503 D(32) 12.0316 6.7893 6.9900

Embodiment 4

A fourth embodiment of the zoom lens comprises, as shown in FIG. 13, the first lens group G1 of positive refractive power, the second lens group G2 of negative refractive power, the third lens group G3 of positive refractive power, the fourth lens group G4 of negative refractive power, and the fifth lens group G5 of negative refractive power serially arranged in order on the closest to an object first basis.

The first lens group G1 is comprised of a cemented lens of two lens pieces, namely, a negative power meniscus lens piece L1 the closest to the object and having its convex surface faced toward the object and a positive power lens piece L2, and a positive power meniscus lens piece L3 having its convex surface faced toward the object.

The second lens group G2 is comprised of a negative power meniscus lens piece L4 the closest to the object and having its front side shaped in aspherical and its rear side shaped in intensely in-curved concave surface, a lens piece L5 the second closest to the object and having its opposite sides shaped in concave surface, a lens piece L6 having its opposite sides shaped in convex surface, and a negative power meniscus lens piece L7 the farthest from the object and having its concave surface faced toward the object.

The third lens group G3 is comprised of a lens piece L8 the closest to the object and having its opposite sides shaped in aspherical convex surface, a lens piece L9 having its opposite sides shaped in concave surface, and a lens piece L10 having its opposite sides shaped in convex surface.

The fourth lens group G4 is comprised of a cemented lens of two lens pieces, namely, a lens piece L11 closer to the object and having its opposite sides shaped in convex surface and a lens piece L12 having its opposite sides shaped in concave surface.

The fifth lens group G5 is comprised of a negative power meniscus lens piece L13 having its concave surface faced toward the image plane, and a positive power meniscus lens piece L14 having its convex surface faced toward the image plane.

The zoom lens in the fourth embodiment, upon varying its operative posture from the wide angle end to the telephoto end to vary magnification, has its first lens group displaced toward the object, its second lens group traversed along the trajectory first coming closer to and then apart from the image plane, its third lens group displaced toward the object, its fourth lens group traversed relative to the third lens group along the trajectory first coming closer to and then apart from the image plane, and its fifth lens group displaced toward the object.

Focusing on an object within close-up photographing range is conducted by displacing the fourth lens group toward the image plane.

The optical data of parameters of the zoom lens in the fourth embodiment are given as follows:

TABLE 10 NS R D Nd νd  1 64.9819 1.3000 1.90366 31.31  2 36.3975 0.0100 1.56732 42.84  3 36.3975 6.6600 1.49700 81.61  4 −1186.1757 0.2000  5 34.2934 4.2232 1.61800 63.39  6 162.5347 D(6)  7 ASPH 33.6698 0.2000 1.51460 49.96  8 36.8067 0.8000 1.91082 35.25  9 8.1262 4.0531 10 −29.8667 0.6500 1.91082 35.25 11 20.0064 0.4000 12 15.8824 2.9802 1.92286 20.88 13 −31.7119 0.7663 14 −16.6818 0.6000 1.77250 49.62 15 −54.0405 D(15) 16 STOP 0.0000 1.2000 17 ASPH 9.0025 3.2330 1.58313 59.46 18 ASPH −17.0238 0.4600 19 −52.2330 0.5000 1.90366 31.31 20 12.6447 1.5345 21 46.2818 2.9182 1.59282 68.62 22 −9.5695 D(22) 23 100.3805 1.2000 1.80518 25.46 24 −28.6956 0.0100 1.56732 42.84 25 −28.6956 0.6000 1.80139 45.45 26 ASPH 19.7020 D(26) 27 −10.7494 0.6300 1.80518 25.46 28 −17.3803 0.2000 29 −4854.1028 2.1691 1.48749 70.44 30 −20.5041 D(30) 31 0.0000 9.8000 32 0.0000 2.8000 1.51680 64.20

The optical data of parameters on the aspherical surfaces are given as follows:

TABLE 11 ASPH ε A4 A6 A8 A10 7 1.0000 −1.81150e−006 −3.53409e−007 2.30973e−009 −1.22024e−011 17 1.0000 −1.28660e−004 1.17974e−006 −4.72888e−008 −2.76128e−009 18 1.0000 4.39407e−004 1.33550e−006 −1.82741e−007 0.00000e+000 26 1.0000 −2.01216e−005 −1.13690e−006 1.04261e−007 −2.22909e−009

Further given below is a varied distance between the specified adjacent pairs of the surfaces of the lens pieces during the zooming in its various stages, that is, with the zoom lens staying at the wide-angle end (f=10.31 mm) being extended to the intermediate focal distance (f=41.50 mm) and up to the telephoto end (f=100.60 mm), and vice versa, together with a focal distance f (in millimeters), F number Fno, and an angle of field ω.

TABLE 12 f 10.31 41.50 100.60 Fno 3.657 5.267 5.799 ω 40.1947 10.9138 4.5726 D(6) 0.9310 19.9590 33.2042 D(15) 19.0512 4.6009 1.6230 D(22) 1.9788 3.7822 0.5120 D(26) 7.0763 5.2729 8.5431 D(30) 0.0000 13.7884 20.1450

Still further given below is a varied distance between the surfaces of the lens pieces from a state where the zoom lens in focus on an object within close-up photographing range stays at the wide-angle end (f=10.31 mm) to another state of its being extended to the intermediate focal length (f=41.50 mm) and up to the telephoto end (f=100.60 mm), together with a focal length f (in millimeters) of the zoom lens in infinity focus and a distance D(0) (in millimeters) from the object to photograph to the foremost or first lens surface:

f 10.31 41.50 100.60 D(0) 919.86 901.49 884.90 D(22) 2.0430 4.3047 2.5769 D(26) 7.0121 4.7504 6.4782

For each of the embodiments described so far, the values to substitute for the terms in the formulae are given as follows:

TABLE 13 Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 βrt 2.911 3.162 2.999 2.502 frt/ft −0.391 −0.460 −0.503 −3.020 β2t/ 4.540 6.759 4.488 4.414 β2w frw/ 2.335 2.760 2.848 3.326 f2

DESCRIPTION OF THE ALPHANUMERIC REFERENCE SYMBOLS STOP Aperture Stop G1 1st Lens Group G2 2nd Lens Group G3 3rd Lens Group G4 4th Lens Group G5 5th Lens Group G6 6th Lens Group 

1. A zoom lens comprising at least five lens groups, namely, the first lens group of positive refractive power, the second lens group of negative refractive power, the third lens group of positive refractive power, the fourth lens group, and the fifth lens group serially arranged in order on the closest to an object first basis, wherein: upon shifting its operative posture from the wide-angle end to the telephoto end to vary magnification, the zoom lens focusing in the wide angle end has its first lens group displaced closer to an object to photograph than it is focusing in the telephoto end, the fourth lens group exhibits negative refractive power, the fifth lens group exhibits negative refractive power, the zoom lens meets the requirement defined in the formula (1) as follows, and the second lens group meets the requirements defined in the formula (3) as follows: 2.502<βrt<3.162  (1) 4.414<β2t/β2w<8.0  (3) where βrt is a composite lateral magnification of all of the lens groups behind the third lens group and closer to the image plane than the same while the zoom lens takes an operative posture at its telephoto end, β2t is a lateral magnification of the second lens group in the zoom lens focusing in the telephoto end, and β2w is a lateral magnification of the second lens group in the zoom lens focusing in the wide angle end.
 2. The zoom lens according to claim 1, wherein the zoom lens meets the requirement defined in the formula (2) as follows: −0.8<frt/ft<−0.3  (2) where frt is a composite focal length of all of the lens groups behind the third lens group and closer to the image plane while the zoom lens takes an operative posture at its telephoto end, and ft is a focal length of the zoom lens at the telephoto end.
 3. The zoom lens according to claim 1, wherein the fourth lens group is displaced toward the image plane for shifting the zoom lens from a state of being in infinity focus to another state of being in focus on an object within close-up photographing range.
 4. The zoom lens according to claim 1, wherein the lens groups behind the third lens group and closer to the image plane than the same meet the requirements defined in the formula as follows: 2.2<frw/f2<3.4  (4) where frw is a composite focal length of the lens groups behind the third lens group and closer to the image plane, and f2 is a focal length of the second lens group.
 5. The zoom lens according to claim 1, further comprising a sixth lens group of positive refractive power disposed immediately behind the fifth lens group and closer to the image plane.
 6. A camera device incorporating image pick-up devices in position closer to the image plane of the zoom lens according to claim 1, for receiving an optical image produced by the zoom lens and converting it into electric signals. 